1) FIOS provides only one WAN IP address. You can have only one router with a WAN connection.
2) You can certainly put two wireless routers behind the FIOS router.
You do not want to disable DHCP in the FIOS router. You will need that for the STBs which will be on the FIOS router's LAN.
Yes, this configuration results in double NAT. That is only an issue if you need to do port forwards. You will need to do port forwards in both routers.
3) Since #2 seems like your best option, I don't see why you would consider #3. This assumes that you want to kepp the two wired and wireless networks separate.